I would very much like to get a bottle (or a case) of wine from a specific vineyard in Germany that is owned by distant cousins of mine but I am having a lot of trouble finding anyone here in the U.S. that sells it and I can't seem to find anyone in Germany that will ship it over here. What is the best way to go about this?

If the wine is not registered here for import, you may have to bribe someone on the far end.
I tried bringing in a French wine that wasn't registered. Even though the importer drove to the vineyard and picked up, he could not get this particular wine without filing for some kind of registration thing which would cost a couple hundred. I eventually gave up. When I go back to that vineyard, I'll buy more.